CRI test and Mcree weighted results

You need to look a bit further. That 700Nm wavelength peak is just one of the peaks used by Chlorophyl. It's not like there is "a photosynthesis" with a 700Nm peak. There are lots of pigments all contributing to photosynthesis and you singled out one of them (chlorophyll) and then even only one chlorophyll variants.

When you combine all systems, the McCree RQE chart shows how efficiently each wavelength is used.
 
Ok. So I read the whole thread. What I take from it is, some say, light intensity or shooting as many photons as possible to the plant, is more efficient than choosing a spectrum where the intensity(photons) may be reduced, because certain spectrums like warm red, require more energy to produce a photon than say a softer blue. Thus, the 2700's are producing more light intensity and delivering more photons more efficiently to the plant. Ok. So, 3500 spectrums produce less photons, yet it is acceptable because, the warm red spectrums produced theoretically are more beneficial to the plant. The plant will use that light more efficiently. So, we use these charts to try to reach some mathematical way of figuring which "efficiency", i.e., more intensity(photons) or better spectrums. Honestly. I think they both would probably work well. Personally. I mix Blurple and HPS. AND have even included CFL in the mix. It works.

This has been a great read actually. Helps me understand(somewhat) back in the day when mono LED lights were advertising their spectrums. And how their spectrums were more beneficial than their competitors. Ah.

Anyway. So, while many of you science guys are trying to figure all this out on paper. And I agree, it might be smart for the gram per watter guys(respect) to throw in some 2,700 and 3,500 or 4,000 whatev. Along with differing CRI's while you discover that holy grail of the perfect light.

Me. I'm just a micro. I think I've decided just to go with 3,500 CRI 90 and blast my few tiny 12/12 from seed plants with 150 watts. Hope for 3 or 4 oz. yield for personal. That's certainly not efficient is it? Except when I do the math it still only costs a few dimes a gram to produce. Probably use the Blurple too. Maybe HPS as well. lol. It's all good.

Nevertheless. I do admire what you do. And I feel these discussions along with more testing and the ever evolving COB tech will only bring us closer to that holy grail. Eventually leading to a few pennies for a gram of top shelf dank. Which outdoor should be achieving anyway.

Thanks science guys and much respect.
 
GrowUrOwnDank said:
Thus, the 2700's are producing more light intensity and delivering more photons more efficiently to the plant. Ok. So, 3500 spectrums produce less photons, yet it is acceptable because, the warm red spectrums produced theoretically are more beneficial to the plant.
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Well actually the 2700K produced the least intensity. 3500K came in second in the par reading and in the middle after the Mcree conversion. How this will actually play out over a plant is still to be determined. 2700K does have the highest conversion factor, so if the intensity of two lamps were the same the 2700K should produce the best. But the conversion factors aren't that different (76 through 80) so the converted readings are indicating it's not worth it at this stage to go with low K high CRI... but again this is all on paper using a metric that may or may not be 100% applicable to the end result.

Cheers.
 
@Rahz have you considered driving the LEDs differently, essentially customizing drive current. Don't know about citi but remember reading about a color shift to warmer cct at lower drive currents for Cree.
 
wietefras said:
You need to look a bit further. That 700Nm wavelength peak is just one of the peaks used by Chlorophyl. It's not like there is "a photosynthesis" with a 700Nm peak. There are lots of pigments all contributing to photosynthesis and you singled out one of them (chlorophyll) and then even only one chlorophyll variants.

When you combine all systems, the McCree RQE chart shows how efficiently each wavelength is used.
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Never said not to use the other wavelengths in the PAR spectrum, and actually, have stated that they are required but we just don't know the optimal amount of it.

What we do know are two things:

1. All wavelengths in the PAR spectrum are involved in photosynthesis
2. Longer wavelength photons are optimal for photosynthetic process

There are other things as well, such as the Emerson Effect and the impact of wavelengths on secondary pigments as you have pointed out. We need further study to determine the impacts for both plant in general and for specific species.
 
PhotonFUD said:
Never said not to use the other wavelengths in the PAR spectrum, and actually, have stated that they are required but we just don't know the optimal amount of it.

What we do know are two things:

1. All wavelengths in the PAR spectrum are involved in photosynthesis
2. Longer wavelength photons are optimal for photosynthetic process

There are other things as well, such as the Emerson Effect and the impact of wavelengths on secondary pigments as you have pointed out. We need further study to determine the impacts for both plant in general and for specific species.
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Hmmmm, like empirical observation of the results of the introduction of differing wavelengths and their combinations, perhaps?

I think you might like to meet a friend of mine, @RM3. He's been doing precisely this for some years now and his work cuts right to the heart of this discussion.

His conclusions call into question many assumptions made about which wavelengths of light are ultimately the most effective for the specific set of desired results.
 
ttystikk said:
Hmmmm, like empirical observation of the results of the introduction of differing wavelengths and their combinations, perhaps?

I think you might like to meet a friend of mine, @RM3. He's been doing precisely this for some years now and his work cuts right to the heart of this discussion.

His conclusions call into question many assumptions made about which wavelengths of light are ultimately the most effective for the specific set of desired results.
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And the only way to determine is through study which there is not enough of. There are a lot of theories on what light does that can be explained by some science however there is much work confirming those theories to be done.

Environmental benefits need to be considered as well. That is another aspect to consider in the debate between the technologies.

For horticultural use, light is not considered differently than any other fuel source. Some fuels are better than others for certain applications. Looking at the automotive industry for example, they have been researching fuel efficiency far much longer than horticultural lighting and are now making a significant technology shift to electric. Why the shift? Because acceptable battery and electrical efficiency has become available at a price point to a market that is growing.

It would be interesting to see how many researchers employed by licensed operators read these forums. Their business model is directly affected by how efficient they can operate and would have an inherent interest in this information. Increased production, reduced production time, and decreased cost of operations all rely on technology. Improved production quality is also a nice to have bonus.
 
PhotonFUD said:
And the only way to determine is through study which there is not enough of. There are a lot of theories on what light does that can be explained by some science however there is much work confirming those theories to be done.

Environmental benefits need to be considered as well. That is another aspect to consider in the debate between the technologies.

For horticultural use, light is not considered differently than any other fuel source. Some fuels are better than others for certain applications. Looking at the automotive industry for example, they have been researching fuel efficiency far much longer than horticultural lighting and are now making a significant technology shift to electric. Why the shift? Because acceptable battery and electrical efficiency has become available at a price point to a market that is growing.

It would be interesting to see how many researchers employed by licensed operators read these forums. Their business model is directly affected by how efficient they can operate and would have an inherent interest in this information. Increased production, reduced production time, and decreased cost of operations all rely on technology. Improved production quality is also a nice to have bonus.
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In theory, theory and practice are the same. In practice, they're not. -Yogi Berra

You got too much theory and analogy running around up there, so much so that when I suggested you ask someone who's spent years doing the very work you bemoan the lack of, you discount it out of hand and then go back to blathering about the car industry?

I'm doing engineering, by definition the profession standing between theory and practice. Empiricism is our stock in trade, and I'll believe what I see over a stack of theories and diagrams any day of the week.

If the theory doesn't explain the facts, then it's time for new theory. Meanwhile, act on the facts!
 
There is a lot of study done and being done on the subject. I know of two parties in the Netherlands doing large scale tests with different spectral distributions (light recipes).

IIRC It"s an EU project even

Outcomes of test so far have shown impact on morphology rather than yield though.
 
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ttystikk said:
In theory, theory and practice are the same. In practice, they're not. -Yogi Berra

You got too much theory and analogy running around up there, so much so that when I suggested you ask someone who's spent years doing the very work you bemoan the lack of, you discount it out of hand and then go back to blathering about the car industry?

I'm doing engineering, by definition the profession standing between theory and practice. Empiricism is our stock in trade, and I'll believe what I see over a stack of theories and diagrams any day of the week.

If the theory doesn't explain the facts, then it's time for new theory. Meanwhile, act on the facts!
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The theory that a light more heavily weighted towards the red region of the PAR spectrum will produce better is based on the finding (or fact) that photosynthesis is more efficient with longer wavelengths.

I don't believe I am discounting anyone or anything. Plant use photosynthesis so it makes sense to understand how photosynthesis functions and use that information as a basis for the theory that we could exploit by emphasising radiant power of higher wavelengths. It is more of discussion on something to study in order to validate.

By no means am I saying what is the absolutely best of anything, there are far too many factors to take into consideration. What works for one person may not work for another since we can't completely replicate environments.

Another member just posted a study on tomatoes grown under different lights with some interesting results.
 
ttystikk said:
Spectrum does not shift significantly with differing drive currents in COB LED.
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Not so sure I agree, even during "binning" citi employs a 3 step McAdams elipse with a plus of minus of something like 175K so two chips marked the same may even have a few percentage points differential. Additionally if the same spectral output (same distribution of photons) can be achieved by underdriving multiple 3000k chips compared to normally driving the 2700k i "theorize" would create less heat distributed over a wider area and be easier control. So as not to cloud the discussion on what is best the question of cost can't really be introduced until you look a actually producing light with desired spectrum and power. Sorry Rahz keep that pocket book open.

I don't have capability to evaluate but guess who does? Thanks for working on this.
 
Also, not being familiar with citi, I'm not seeing any destinction for actual output (lumens) like cree does. Does citi just throw out any that are outside a specif range? Sure would help of there were an industry standard here.

Edit - found it 85% threshold from what they call an initial value S. So they discard based on a comparison to the chip itself? And rely on the output being above the minimum specified. Since the testing is done at 1650ma and they can handle over 4000ma seems that there are enough variables at play that are unevaluated bc the chip has 60 percent more "capacity" than what they test at. As always please correct my incorrectness.
 
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I'd like to see y'alls discussion on if light is a particle or is it a quantum packet of waves. I can be convinced that drive current wouldnt impact color temp significantly because that would make the units unpredictable. But what about the quantum packets of photons that make up the light? Show the numbers.
 
SSGrower said:
I'd like to see y'alls discussion on if light is a particle or is it a quantum packet of waves. I can be convinced that drive current wouldnt impact color temp significantly because that would make the units unpredictable. But what about the quantum packets of photons that make up the light? Show the numbers.
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Huh?
 
A semiconductor wI'll emit light based on the materials and methods of construction and energy input. The light emitted is the result of subatomic particles retiring to their original or stable energy states after being excited. Since we are talking of semiconductors that have alloys in them there is a potential for multiple energies of photons to be emmited. Hence we see a spectrum of light vs. a pure color.

I should say alloys and other proprietary materials of construction the manufacturers won't pubulish.
 
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SSGrower said:
@Rahz have you considered driving the LEDs differently, essentially customizing drive current. Don't know about citi but remember reading about a color shift to warmer cct at lower drive currents for Cree.
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There is a slight color shift, but looking at the various Mcree factors that were tabulated, shifting the spectrum via drive current will produce a much smaller variance than shifting from one K/CRI to another.
 
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